1. Field of the Invention
The present invention relates to a novel diphosphine compound characterized by introducing an oxygen-containing functional group bonded via an oxygen atom such as an alkoxy group to the benzene rings of an optically active diphosphine compound having two benzene rings of a biphenyl skeleton at the 4- and 4′-positions thereof, a transition metal complex containing said diphosphine compound, a catalyst for an asymmetric synthesis comprising said transition metal complex, and a method for producing an optically active compound characterized by subjecting an unsaturated compound to an asymmetric reduction in the presence of said transition metal complex.
2. Description of the Related Art
Recently, an asymmetric synthesis using a transition metal complex containing a diphosphine ligand has been desired a formulation of various diphosphine ligands so as to improve the performance of the reaction. Patent literature 1, for example, discloses various diphosphine ligands having a ((5,6),(5′,6′)-bis(methylenedioxy)biphenyl-2,2′-diyl) group, specifically ((5,6),(5′,6′)-bis(methylenedioxy)biphenyl-2,2′-diyl)bis(diphenylphosphine) (hereinafter referred to as SEGPHOS).
Patent literature 2 describes an asymmetric diphosphine compound introducing a methoxy group to a benzene ring that is different from methylenedioxybenzene, however, it does not describe an example of synthesis of the asymmetric diphosphine compound introducing a methoxy group, nor an example of synthesis of a symmetric diphosphine compound introducing a methoxy group, nor a reaction example of an asymmetric hydrogenation using the diphosphine compound as a ligand.
Non-patent literature 1 describes synthesis of a SEGPHOS derivative formed by substituting a methylene proton of methylenedioxybenzene with fluorine and its application to asymmetric hydrogenation as a ruthenium complex, but does not show any practical data thereof. Non-patent literature 2 describes synthesis of a SEGPHOS derivative formed by substituting a methylene proton of methylenedioxybenzene with an alkyl group and its application to asymmetric hydrogenation as a ruthenium complex, but hardly contributes to improvement of asymmetric recognition.
Patent literature 3 describes a ligand substituting at the 3- and 3′-positions, and patent literature 2 describes a ligand having different modes of substitution in two benzene rings, however, both ligands have a complicated synthesis route and are difficult to use industrially due to an insufficient substrate/catalyst ratio of about 100 in the symmetric hydrogenation.    Patent literature 1: JP-A-10-182678    Patent literature 2: WO 02/40492 pamphlet    Patent literature 3: WO 02/40491 pamphlet    Non-patent literature 1: Synthesis, 2004, 326    Non-patent literature 2: Tetrahedron: Asymmetry, 2004, 15, 2185